The BGS Lexicon of Named Rock Units — Result Details

Heavitree Breccia Formation

Computer Code: HVBR Preferred Map Code: HvBr
Status Code: Full
Age range: Permian Period (P) — Permian Period (P)
Lithological Description: Reddish brown, mainly fine-grained, breccia; clasts (mainly less than 8cm, some 30cm+) of Culm sandstone, vein quartz, hornfels lava, granite, and potassium feldspar (Murchisonite). Well cemented locally.
Definition of Lower Boundary: Overlies Alphington Breccia; defined by marked increase in amount of Murchisonite feldspar. Basal beds form a prominent scarp over the less well cemented Alphington Breccia.
Definition of Upper Boundary: From Exminster southwards Heavitree Breccia is overlain by and interdigates with the Dawlish Sandstone. North of Exminster Heavitree Breccia is overlain fairly sharply by Dawlish Sandstone. In the Hill Barton area (SX 956 928) thin Heavitree Breccia is overlain fairly sharply by Monkerton Formation.
Thickness: 135-300m
Geographical Limits: Outcrops in and south of Exeter between Heavitree, Exminster and Kennford.
Parent Unit: Exeter Group (EXE)
Previous Name(s): Exminster Breccias [Obsolete Name And Code: Use HVBR] (EXBR)
Heavitree Breccia (*319)
Heavitree Breccia Member (-970)
Kennford Breccias And Langstone Breccia (-971)
Conglomerates Of Heavitree (-334)
Coryton Breccias (-1607)
Exminster Conglomerates (-2251)
Heavitree Conglomerate (-2252)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Area  Heavitree, Exeter. Heavitree quarry (also known as "East Wonford Quarry"). Well cemented fine- to medium-grained breccia in beds 0.2 to 1.0m thick. 
Reference(s):
Smith, D B, Brunstrom, R G W, Manning, D I, Simpson, S and Shotton, F W. 1974. A correlation of Permian rocks in the British Isles. Geological Society of London Special Report No. 5. 
De La Beche, H T, 1939. Report on the geology of Cornwall, Devon and west Somerset. Memoir of the Geolgoical Survey. 
Murchison, R I, 1867. Siluria. 4th Edition. London: Murray 
Worth, R N, 1890. The igneous constituents of the Triassic of the Geological Society of London, Vol.46, p.69-83. 
Ussher, W A E, 1902. The Geology of the country around Exeter. Memoir of the Geological Survey of Great Britain, Sheet 325. (England and Wales). 
Laming, D J C, 1982. The New Red Sandstone. "In" Durrance, E M and Laming, D J C, (Editors). The Geology of Devon, p.148-177. 
Laming, D J C, 1968. New Red Sandstone stratigraphy in Devon and West Somerset. Proceedings of the Ussher Society, Vol.2, p.23-25. 
Bristow, C R, 1984. Geological notes and local details for 1:10 000 Sheet SX98NW (Exminster, Devon). 
Bristow, C R and Scrivener, R C, 1984. The stratigraphy and structure of the Lower New Red Sandstone of the Exeter district. Proceedings of the Ussher Society, Vol.6, p.68-74. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E325